[Chandler-dev] Pre-loading items as a performance optimization

[Morgen Sagen]

On Oct 4, 2006, at 3:30 PM, Grant Baillie wrote:

> On 4 Oct, 2006, at 14:37, Morgen Sagen wrote:
>
>> I did try replacing those mStart and mEnd calls like this:
>>
>>    testVal = getattr(EventStamp(view[key]), startAttrName)
>>
>> with calls like this:
>>
>>    testVal = view.findValue(key, getattr(EventStamp,  
>> startAttrName).name)
>>
>> to avoid loading, but overall a similar number of items was being  
>> loaded anyway (32 items loaded versus 34, if I recall).  Also,  
>> there are some cases where findValue( ) doesn't work -- when an  
>> attribute is Calculated, the item needs to be loaded and getattr  
>> used.
>
> True, but you can refactor the Calculated to work with  
> view.findValues(). This is hard to do in the general case, but it  
> turns out that those mStart() and mEnd() functions are only ever  
> called with a startAttr of 'effectiveStartTime' and endAttr of  
> 'effectiveEndTime'.

Right -- rather than reimplementing Calculated, I did this:

         try:
             testVal = view.findValue(key, getattr(EventStamp,  
startAttrName).name)
         except AttributeError:
             # Guess we have to load the item, since findValue can't  
retrieve a
             # Calculated
             testVal = getattr(EventStamp(view[key]), startAttrName)

The exception only happened a few times (for those 'effective'  
times), but overall there wasn't much change to the timings.